I went a slightly different route, but this is nice and simple.

I've been using these on a few printers for a long while now and I'm very happy with them. Depending on which board you have, this may be a tight fight.
Print the parts, supports are designed in for the Bottom. Top doesn't need supports, just print it flat.
Once printed, line up the Bottom portion to ensure it is straight, and make three mount holes in the frame with a pencil. Drill out the three holes to accept M3 screws, then slide the PSU into the cradle. Place the Top part over your desired location, but do not cover the venting slits to allow proper cooling of the unit. Mark the two mounting holes as you did with the lower, remove the Supernight, and drill the holes for the Top. After the top is locked in the secured, you can now drop in the PSU.

Hardware needed:
*5 M3x12mm socket cap screws, but M3x16mm should work fine so long as they don't interfere with the Z platform
*5 M3 nuts.
If you like it, thank Jagowilson for inspiring me to share the design.